Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 


Tornadoes – how frequently do they hit New Zealand?

Tornadoes – how frequently do they hit New Zealand?

Tornadoes, like the one that hit Auckland’s western suburbs today, are relatively rare events in New Zealand.

On average there are around seven moderate to strong tornado events reported in New Zealand each year.

NIWA meteorologist, Dr Richard Turner, says “fatalities associated with tornadoes are rare in New Zealand, with the most recent cases being the Albany tornado last year, which killed 1 person, and a tornado near Waitara in August 2004 which killed 2 people.”

“Auckland is hit by a tornado on average less than once per year, but there is considerable variability from year to year with some years getting none,” says Dr Turner.

New Zealand tornadoes are neither as common nor as destructive as those that occur over the plains of the United States, but even small scale tornadoes, like today’s event can cause damage, injury and even deaths. The west coast of the South Island and the North Island coast from Taranaki to Northland have been particularly affected by tornadoes in the past.

Tornadoes in New Zealand are usually around a few tens of metres wide and have tracks of just a couple of kilometres. They are extremely localised and the damage is very confined to the actual tornado itself.

A tornado will typically last for a few minutes, track across the land for 2 to 5 kilometres and will have a diameter of 20 to 100 metres. Wind speeds are in the order of 115 to 180 km/h. At the more extreme end, some tornadoes track for over 100 kilometres, are over 1 kilometer wide and have winds up to 480 km/h – such tornadoes are extremely rare, anywhere in the world.

Dr Turner says “In New Zealand most tornadoes are associated with pre-frontal squall lines - bands of thunderstorms embedded in strong unstable pre-frontal northwesterly flow.”

“The thunderstorms have very strong updrafts and if these occur in an environment in which the wind directions rotate as the air rises, the updraft can start to spin and a mesocyclone can form. It is from these mesocylcones, that can be as little as 1-2 kilometres across, that tornadoes are spawned.”

NIWA maintains a catalogue of major weather events in New Zealand over the last 200 years called the New Zealand Historic Weather Events Catalogue.

The information has been collated from newspaper reports, journals, books and databases kindly provided by various organisations and individuals. For each event we identify the regions affected, the hazards types associated with the event and the resulting impacts.

The most damaging and lethal tornado in New Zealand occurred at Frankton (Hamilton) on 25 August, 1948. The tornado carved a 100–200 m swath through the suburb, causing 3 deaths, 12 injuries, damaging 150 houses and 50 businesses with an overall damage cost of $60 million.

The most recent events occurred on the west coast of the North Island, when a swarm of at least 12 tornadoes hit the Taranaki Coast on Wednesday the 4th and Thursday the 5th of July 2007 causing widespread damage in the region.

Oakura, a town 12 km southwest of New Plymouth was most affected. Roughly 50 houses suffered major damage, some of it irreparable, when two tornadoes ripped through the town.

Last year, a tornado in the Auckland suburb of Albany killed one person, sent cars airborne and did about $10 million in damage over a 15 km path.

Many other tornadoes in remote rural areas will be unreported.

Current research at NIWA is investigating very high resolution weather forecast models (which demand huge computational resources) ability to predict the occurrence of mesocyclones. If successful, this could potentially aid forecasters in their ability to identify mesocyclone formation between 6 and 12 hours in advance, increasing warning times.

ENDS

More information:

What are the warning signs of a tornado?
• Hail or heavy rain followed by dead calm or a fast, intense wind shift.
• Hail stone size can indicate storm intensity.
• Load continuous roar or rumble, much like the sound of an approaching freight train.
• At night, small, bright, blue-green to white flashes at ground level near a thunderstorm.
• A large, dark, low-lying cloud.
• Dark, often greenish sky.
• Cloud of debris. An approaching cloud of debris can mark the location of a tornado even if a funnel is not visible.

For more information go to: http://www.niwa.co.nz/natural-hazards/hazards/extreme-weather-winds-and-tornadoes

© Scoop Media

 
 
 
 
 
Business Headlines | Sci-Tech Headlines

 

Half Full: Dairy Payouts Steady, Cash Will Be Tight

Industry body DairyNZ is advising farmers to focus on strong cashflow management as they look ahead to the 2015-16 season following Fonterra's half-year results announcement today. More>>

ALSO:

First Union: Cotton On Plans To Use “Tea Break” Law

“The Prime Minister reassured New Zealanders that ‘post the passing of this law, will you all of a sudden find thousands of workers who are denied having a tea break? The answer is absolutely not’... Cotton On is proposing to remove tea and meal breaks for workers in its safety sensitive distribution centre. How long before other major chains try and follow suit?” More>>

ALSO:

Scoop Business: NZ-Korea FTA Signed Amid Spying, Lost Sovereignty Claims

A long-awaited free trade agreement between New Zealand and South Korea has been signed in Seoul by Prime Minister John Key and the Korean president, Park Geun-hye. More>>

ALSO:

PM Visit: NZ And Viet Nam Agree Ambitious Trade Target

New Zealand and Viet Nam have agreed an ambitious target of doubling two-way goods and service trade to around $2.2 billion by 2020, Prime Minister John Key has announced. More>>

ALSO:

Scoop Business: NZ Economy Grows 0.8% In Fourth Quarter

The New Zealand economy expanded in the fourth quarter as tourists drove growth in retailing and accommodation, and property sales increased demand for real estate services. More>>

ALSO:

Scoop Business: RBNZ’s Wheeler Keeps OCR On Hold, No Rate Hikes Ahead

The Reserve Bank has removed the prospect of future interest rate hikes from its forecast horizon as a strong kiwi dollar and cheap oil hold down inflation, and the central bank ponders whether to lower its assessment of where “neutral” interest rates should be. The kiwi dollar gained. More>>

ALSO:

Get More From Scoop

 
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news